public interface IList {
    void addFirst(int data);
    void addLast(int data);
    void addIndex(int index,int data);
    boolean contains(int key);
    void remove(int key);
    void removeAllKey(int key);
    MySingleList.ListNode middleNode();
    MySingleList.ListNode middleNode1();
    MySingleList.ListNode reverseList();

    int size();
    void clear();
    void display();


}